Aliens disguised as humans plot to conquer Earth from a Godzilla-themed tower in a Tokyo amusement park, summoning the monsters Gigan and King Ghidorah to destroy the planet's cities ahead of colonization. A manga artist uncovers the scheme and uses a recorded roar to summon Godzilla and Anguirus to fight back. Made on a reduced budget with substantial stock footage recycled from earlier entries in the series.